This invention relates to regulated voltage supply circuits and, more particularly, to an integrated circuit (IC) voltage regulator capable of producing a direct current voltage the magnitude and temperature coefficient of which can be set to predetermined values.
Prior art voltage regulators commonly include a pair of transistors operated at different current densities. The two transistors are interconnected with associated circuitry so as to develop a voltage therebetween that is proportional to the difference in the respective base-to-emitter voltages (.DELTA.V.sub.be). This difference voltage is used to set the current in the emitter of one of the transistors and has a positive temperature coefficient (TC). The thermal emitter current is utilized to produce a voltage that varies directly with absolute temperature which, in turn, is combined with a negative TC voltage to produce a combined voltage having a substantially zero TC.
Although such prior art regulators have significant advantages most, if not all, suffer from serious limitations. For instance, to prevent errors in the thermal current that may be caused by differences in the collector-to-emitter voltages of the two transistors, prior art regulators require complex feedback schemes to inhibit mismatch of the two devices. These schemes are not desirable in the design of integrated circuits as undue chip area is required. Additionally, the voltage level and temperature coefficient of the output regulated voltage of these prior art regulators can not be independently set but rather are determined by the magnitude of the difference voltage .DELTA.V.sub.BE. Moreover, prior art regulators can not generate adjustable TC regulated voltages less than the value of a transistor V.sub.BE voltage.
Hence, a need exists for a regulator circuit that does not suffer from the aforementioned limitations of the prior art regulators and which does not require complex feedback circuitry to provide an output voltage that can be set to any voltage and temperature coefficient.